Safety apparatus of air impact driver

ABSTRACT

A nose ( 5 ) of an air impact driver ( 1 ) is mounted with a slidable contact nose ( 12 ) and by the contact nose, a contact valve ( 23 ) upward therefrom is operated to switch. An AND circuit operated to pilot an air motor controlling pilot valve ( 39 ) and a piston controlling pilot valve ( 41 ) is constituted by a trigger valve ( 8 ) operated by a trigger lever ( 9 ) and the contact valve ( 23 ). When the contact nose is pressed and the trigger lever is pulled, the air motor controlling pilot valve and the piston controlling pilot valve are switched to starting positions to start the air impact driver.

TECHNICAL FIELD

The present invention relates to a safety apparatus for preventing anair impact driver from being started by erroneous operation,particularly relates to a safety apparatus of an air impact driverconstituted by a pneumatic circuit.

BACKGROUND ART

An air impact driver provided for screwing a building material of aplaster board or the like is mounted with a mechanical type safetyapparatus by a contact arm similar to a nail striker. The contact arm isan arm formed in a crank-like shape along outer shapes of a nose and acylinder housing of the air impact driver which is slidable in parallelwith the nose, a front end thereof is projected frontward from the noseand other end reaches a front face of a trigger lever of a main body ofthe air impact driver.

A trigger lever is attached with a pivotable free arm and when thecontact arm is pressed to a side of the main body of the air impactdriver, a front end portion of the free arm attached to the triggerlever is pressed by the contact arm to be proximate to a stem of atrigger valve. When the trigger lever is pulled under the state, thefree arm is pivoted in a direction of the trigger valve by constitutinga fulcrum by the front end portion along with the trigger lever and thestem of the trigger valve is pressed by the free arm to start the airimpact driver. Further, even when first, the trigger lever is pulled andthereafter the contact arm is pressed to an object face of screwing, thefree arm presses the stem of the trigger arm to start to the air impactdriver similar to the above-described operation.

In this way, the trigger lever and the contact arm are constituted tocooperatively make the trigger valve ON, when only the trigger lever isoperated, the free arm does not reach a position of the stem of thetrigger arm and the air impact driver cannot be started to therebyprevent the air impact driver from being started by erroneouslyoperating the trigger lever.

According to the mechanical type safety mechanism of the aboveconventional art, the contact arm passes a side face of thecylinder-housing and therefore, a width of a total of the air impactdriver is widened and there is a case in which it is difficult to strikea screw to a corner portion or a location having a narrow width.Further, according to the constitution in which the front end of thefree arm attached to the trigger lever is pressed up by sliding thecontact arm and the total of the free arm is moved by pulling thetrigger lever to thereby press the stem of the trigger valve, thereposes a problem that the stroke of pressing the contact arm is prolongedand therefore, operability is not excellent, further, operation of onecycle is devoid of swiftness.

Further, as other problem, there is a case in which the contact armcannot be slid by clogging a plaster powder produced in screwing betweena slide guide supporting the long contact arm and the contact arm andwhen the contact arm is not returned from a pressing position to aninitial position, there poses a problem that when the trigger lever iserroneously operated, the air impact driver is started and the safetymechanism does not function.

DISCLOSURE OF THE INVENTION

A technical problem to be resolved is posed for providing an air impactdriver improving difficulty in fastening screw to a corner portion or anarrow portion and general operability owing to the above-describedproblem and it is an object of the invention to resolve theabove-described problem.

The invention is proposed in order to achieve the above-described objectto provide a safety apparatus of an air impact driver mounting aslidable contact nose to a nose of the air impact driver, providing acontact valve operated to switch by moving to slide the contact nose,constituting an air pressure logic circuit for controlling a startingcontrol valve of the air impact driver by a trigger valve operated by atrigger lever and the contact valve and providing a pneumatic signal tostart the air impact driver when the trigger lever and the contact valveare switched to ON positions by pulling the trigger lever.

Further, the invention provides a safety apparatus of an air impactdriver mounting a slidable contact nose to a nose of the air impactdriver, connecting a contact valve to the contact nose, providing an airpressure logic circuit for controlling a starting control valve of theair impact driver by a trigger valve operated by a trigger lever and thecontact valve, providing a pneumatic signal to start the air impactdriver when the contact nose is pressed and the trigger valve and thecontact valve are switched to ON positions by pulling the trigger lever,wherein the contact valve is a switch valve communicating a secondaryside outlet to a primary side inlet at an ON position and communicatingthe secondary side outlet to an atmosphere at an OFF position.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a standby state of an air impactdriver showing an embodiment of the invention.

FIG. 2 is a sectional view of a state of operating a contact nose of theair impact driver ON.

FIG. 3 is a sectional view of a state of operating the contact nose anda trigger lever of the air impact driver ON.

FIG. 4 is a sectional view showing a state of finishing to fasten ascrew by the air impact driver.

FIG. 5( a) through FIG. 5( e) are sectional views showing steps ofoperating an impact mechanism.

FIG. 6 is a sectional view of an initial state of a contact valve.

FIG. 7 is a sectional view of a state of making the contact valve ON.

FIG. 8 is a sectional view showing an initial state of a contact valvewhich is not subjected to an erroneous starting preventing measure.

FIG. 9 is a sectional view showing a state of making the contact valveof FIG. 8 ON.

FIG. 10 is a sectional view of a state of returning from the state ofmaking the contact valve of FIG. 8 ON to the initial state.

FIG. 11 is a sectional view of an initial state of a contact valveshowing other embodiment of the invention.

FIG. 12 is a sectional view showing a state of making the contact valveof FIG. 11 ON.

FIG. 13 is a sectional view of an initial state of a contact valveshowing other embodiment of the invention.

FIG. 14 is a sectional view showing a state of making the contact valveof FIG. 13 ON.

Further, in notations in the drawings, numeral 1 designates an airimpact driver, numeral 5 designates a nose, numeral 8 designates atrigger valve, numeral 9 designates a trigger lever, numeral 12designates a contact nose, numeral 13 designates an air cylinder,numeral 14 designates a piston, numeral 15 designates a hexagonal shaft,numeral 17 designates an impact mechanism, numeral 19 designates an airmotor, numeral 22 designates a rod, numeral 23 designates a contactvalve, notation 23 a designates a spool, numeral 33 designates an airmotor switch valve, numeral 39 designates an air motor controlling pilotvalve, numeral 41 designates a piston controlling pilot valve, numeral52 designates a poppet valve, numeral 71 designates a contact valve,numeral 72 designates a cylinder portion, numeral 73 designates a spool,numeral 81 designates a contact valve, numeral 82 designates a cylinderportion, numeral 83 designates a vent hole and numeral 84 designates aspool.

BEST MODE FOR CARRYING OUT THE INVENTION

A detailed description will be given of an embodiment of the inventionin reference to the drawings as follows. FIG. 1 through FIG. 4 show theair impact driver 1 which is constituted by a cabinet structureconnected with an air motor housing 2, a clutch housing 3, a cylinderhousing 4, and the nose 5 in one row from above and attached with a grip6 extended from the clutch housing 3 in a direction orthogonal thereto.Similar to a general pneumatic tool, an air plug is attached to an endportion of the grip 6 although illustration thereof is omitted, an airhose is connected to the air plug and high pressure air is supplied froman air compressor to an air chamber 7 at inside of the grip 6. A baseportion of the grip 6 is provided with the trigger valve 8 and thetrigger lever 9 and the air impact driver 1 is started and stopped byopening and closing the trigger valve 8 by operating the trigger lever9.

A back face (right side of drawing) of the nose 5 is provided with aknown connecting screw feeding apparatus comprising a spring offset typeair cylinder 10 and a feed claw 11 connected to a piston rod thereof anda connecting screw at inside of a connecting screw magazine (notillustrated) is fed into the nose 5 by moving the feeding claw 11forward and rearward in cooperation with one cycle operation of the airimpact driver 1. Further, a portion A on a right upper side of thedrawing is the sectional view viewing a portion of the trigger valve 8from a right side, a portion B on a left lower side thereof is asectional view viewing a portion of the contact nose 12 from a left sideand air pipes are indicated by chain lines.

The piston 14 of the air cylinder 13 included in the cylinder housing 4is attached with the driver bit 15 at a front face (lower side of thedrawing) thereof and attached with the hexagonal shaft 16 at a back face(upper side of the drawing) thereof. The impact mechanism 17 of acentrifugal meshing type is included in the clutch housing 3, ahexagonal hole is formed at a center of a driven rotating member 18(hereinafter, referred to as anvil) having a horizontal section in abutterfly-like shape arranged at a center thereof and the hexagonal holeis penetrated by the hexagonal shaft 16. The rotor 20 of the air motor19 arranged above the impact mechanism 17 is provided with a center holehaving a diameter larger than that of the hexagonal shaft 16 and anupper portion of the hexagonal shaft 16 advances into the center hole.The piston 14 and the driver bit 15 and the hexagonal shaft 16 arerotated around an axis along with the anvil 18 of the impact mechanism17 and made to be liftable at inside of the air cylinder 13.

Impact operation by the air motor 19 and the impact mechanism 17 is wellknown and the rotor 20 of the air motor 19 is coupled to an outer rotor21 of the impact mechanism 17 and the both members are integrallyrotated. As shown by FIG. 5( a), the outer rotor 21 is pivotablyattached with a hammer 21 a of a lever type. When the outer rotor 21 isstarted to rotate in the clockwise direction of the drawing, a rear sidein a rotational direction of the hammer 21 a is pivoted in a rotationalcenter direction by static inertia and a corner portion of the rear sideis brought into contact with the anvil 18 as shown by FIG. 5( b) andrides over a projected portion of the anvil 18 to be pushed out to anouter side reverse to the side in starting as shown by FIG. 5( c).Thereby, as shown by FIG. 5( d), a corner portion on a front side in therotational direction thereof is pivoted in the rotational centerdirection to be brought in mesh with the projected portion of the anvil18 to rotate while impacting the anvil 18. Further, by rotating theanvil 18, as shown by FIG. 5( e), the corner portion of the front sideof the hammer 21 a is detached from the anvil 18 and as shown by FIG. 5(b), the corner portion on the rear side is brought into contact with theanvil 18. In the following, the hammer 21 a is circulated at high speedin a swinging cycle of FIG. 5( b) through FIG. 5( e) to continuouslystrike the anvil 18 in the rotational direction to thereby rotate thehexagonal shaft 16 and the piston 14 and the driver bit 15.

Next, the contact nose 12 of FIG. 1 will be explained. The contact nose12 fitted to an outer peripheral face of a front end portion of the nose5 can be slid upwardly relative to the nose 5. The contact nose 12 isattached with the rod 22 to direct to an upper side thereof and a frontend of the rod 22 is brought into a rod guide hole of the contact valve23 provided at a lower portion of the cylinder housing 4 to be broughtinto contact with a stem 24 at inside of the rod guide hole.

A stroke adjusting dial 25 is attached to a center of a front face ofthe contact nose 12 and a stopper 26 formed at the nose 5 is disposedupward from the stroke adjusting dial 25. A rear face of the strokeadjusting dial 25 is formed with a cam portion 27 a radius from arotational center of which is changed in steps (8 steps in theillustrated example) by a rotational angle thereof. A clip stopmechanism of 8 steps is formed by springs (not illustrated) and balls 28inserted into holes at a rear face of the stroke adjusting dial 25 andball receiving holes 29 aligned in a ring-like shape at a front face ofthe contact nose 12 to thereby fix the stroke adjusting dial 25 at everyconstant rotational angle.

The stopper 26 provided at the nose 5 is opposed to an outer peripheralface of the cam portion 27 of the stroke adjusting dial 25 and when thecontact nose 12 is slid to an upper side, the outer peripheral face ofthe cam portion 27 is brought into contact with the stopper 26 to stopthe contact nose 12. As described above, the radius of the cam portion27 brought into contact with the stopper 26 differs by the rotationalangle of the stroke adjusting dial 25 and therefore, a stroke of slidingthe contact nose 12 to the upper side can be adjusted in 8 steps byrotating the stroke adjusting dial 25 to arbitrary click positions,thereby, a depth of fastening the screw can be adjusted.

Successively, an explanation will be given of a pneumatic circuit and anoperational stroke of the air impact driver 1. FIG. 1 shows a standbystate, a stem 30 of the trigger valve 8 is moved down to a closedposition and a puppet 31 coaxial with the stem 30 is moved up by aspring and a pneumatic pressure operated to a lower face thereof.

An intake port 32 of the air motor 19 is connected with the air motorswitching valve 33, an input port 34 of the air motor switching valve 33is connected to an upper output port 35 of the trigger valve 8, an upperpilot port 36 is connected to an upper output port 37 of the triggervalve 8 shown in the portion A, and a lower pilot port 38 is connectedto the air motor controlling pilot valve 39.

An upper pilot port 40 of the air motor controlling pilot valve 39 andan upper pilot port 42 of the piston controlling pilot valve 41 on theleft are connected to the upper output port 37 of the trigger valve 8shown in the portion A.

An upper port 43 of the air cylinder 13 and a front port 44 of thespring offset type air cylinder 10 of the connecting screw feedingapparatus are connected to the lower port 45 of the piston controllingpilot valve 41 and a lower port 46 of the air cylinder 13 is connectedto a lower port 47 of the trigger valve 8 shown in the portion A.

A lower port 48 of the contact valve 23 arranged at a lower portion ofthe cylinder housing 4 is connected to an upper port 49 of the pistoncontrolling pilot valve 41 and an upper port 50 of the contact valve 23is connected to an air chamber connecting port 51 shown in the portionA.

The lower port 48 of the contact valve 23 and the small-sized poppetvalve 52 arranged to be contiguous to the contact valve 23 arecommunicated via a clearance at an outer periphery of the contact valve23 and the poppet valve 52 opens and closes a path 54 communicating withan upper port 53 of the motor controlling pilot valve 39.

In further details, as shown by FIG. 6, the small-sized poppet valve 52arranged to be contiguous to the contact valve 23 and the lower port 48of the contact valve 23 are communicated via the clearance at the outerperiphery of the contact valve 23 and the poppet valve 52 opens andcloses the path 54 to the upper port 53 of the air motor controllingpilot valve 39. The spool 23 a of the contact valve 23 is formed with anexhausting path 23 b communicating an outer peripheral face of a middleportion thereof to a bottom face thereof on a side of the stem 24 and atan initial position shown in FIG. 6, the lower port 48 constituting asecondary side path is communicated with the atmosphere via theexhausting path 23 bof the spool 23 a.

As shown by FIG. 1 and FIG. 6, in the initial state (state at a standbyposition) in which the trigger valve 8 is disposed at a closed positionand the contact noses 12 is moved down, high pressure air in the airchamber 7 is supplied from the lower port 47 of the trigger valve 8 to alower air chamber via the lower port 46 of the air cylinder 13 to pushup the piston 14 to an upper standby position.

FIG. 2 and FIG. 7 show a state of bringing the contact nose 12 intocontact with an object face of screwing to press, the spool 23 a of thecontact valve 23 is pushed up by the rod 22 of the contact nose 22 tocommunicate the upper port 50 and the lower port 48, pressurized air issupplied to an air chamber of the piston controlling pilot valve 42 viathe lower port 48, as shown by FIG. 2, a spool of the piston controllingpilot valve 41 is moved up to cut the upper port 49 and the lower port45. Further, simultaneously therewith, pressurized air pushes up thepoppet valve 52 via the path of the outer periphery of the contact valve23, pressurized air is supplied to an air chamber of the air motorcontrolling pilot valve 39 via the output path 54, and a spool is movedup to maintain a state of cutting the upper port 53 and the lower port55.

Successively, when the trigger lever 9 is pulled as shown by FIG. 3, thestem 30 of the trigger valve 8 is moved up to communicate the upperports 35, 37 of the trigger valve 8, pressurized air operated to a lowerface of the poppet 31 is exhausted from a surrounding of the stem 30 toa lower side to move down the poppet 31 and air at the lower air chamberof the air cylinder 13 is exhausted to the atmosphere via the triggervalve 8.

Further, pressurized air is supplied to the input port 34 of the airmotor switching valve 33 via the upper port 35 of the trigger valve 8,and a pilot pressure is applied to the upper pilot port 36 of the airmotor switching valve 33, the pilot port 40 of the air motor controllingpilot valve 39 and the pilot port 42 of the piston controlling pilotvalve 41. Thereby, the spool of the air motor switching valve 33, thespool of the air motor controlling pilot valve 39 and the spool of thepiston controlling pilot valve 41 are moved down, pressurized air issupplied from the lower port 48 of the contact valve 23 disposed at thelower portion of the cylinder housing 4 to an upper air chamber of theair cylinder 13 via the piston controlling pilot valve 41, and thepiston 14 and the driver bit 15 and the hexagonal shaft 16 start movingdown.

Further, pressurized air is supplied to the lower pilot port 38 of theair motor switching valve 33 via the lower port 55 of the air motorcontrolling pilot valve 39, the spool 56 of the air motor switchingvalve 33 is moved up and after moving down the piston 14, the air motor19 is started and the piston 14 and the driver bit and the hexagonalshaft 16 start rotating, when the air motor 19 is started, the anvil 18and the hexagonal shaft 16, the piston 14, the driver bit 15 are rotatedby high speed impact operation of the impact mechanism 17 and the screwis fastened to the object of screwing.

FIG. 4 shows a state of finishing to screw and the piston 14 reaches alower end of a movable range to push down a bumper 57 at inside of theair cylinder 13 and the poppet valve 52 at a bottom portion thereof. Bymoving down the poppet valve 52, pressurized air supplied to the lowerair chamber of the air motor switching valve 33 via the air motorcontrolling pilot valve 39 is exhausted from the trigger valve 8 via thepoppet 52 and the lower port 46 of the air cylinder. Thereby, the airpressure operated to the lower face of the spool 56 of the air motorswitching valve 33 is reduced to move down the spool 56 and the inputport 32 of the air motor 19 and the air chamber 7 are cut to stoprotating the air motor 19.

When the trigger lever 9 is released after finishing to fasten to screw,the stem 30 of the trigger valve 8 is moved down to the initialposition, pressurized air is brought into the lower face of the poppet31 to move up the poppet 31, pressurized air is supplied from the airchamber 7 to the lower air chamber of the air cylinder 13 via the lowerport 47 of the trigger valve 8 and the piston 14 is moved up to returnto the initial position.

Next, an explanation will be given of a case of operating to switch ononly the trigger lever 9 in the initial state shown in FIG. 1. When thetrigger valve 8 is switched on by operating the trigger lever 9, thepilot pressure is applied to the respective upper pilot ports 36, 40, 42of the air motor switching valve 33 and the air motor controlling pilotvalve 39 and the piston controlling pilot valve 41 and the respectivespools of the air motor controlling pilot valve 39 and the pistoncontrolling pilot valve 41 are moved down to open positions.

At this occasion, since the contact valve 23 operated by the contactnose 12 stays to be in the initial state, pressurized air is notsupplied to the motor controlling pilot valve 30 and the pistoncontrolling pilot valve 41 and the air motor 19 (and the air cylinder13) stay to be in a stationary state. Further, pressurized air is notsupplied from the air motor controlling pilot valve 39 to the lowerpilot port 38 of the air motor switching valve 33 in cooperation withoperation of the piston controlling pilot valve 41 and therefore, thespool 56 of the air motor switching valve 33 is moved down by the pilotpressure applied to the upper pilot port 36 to cut the input port 32 ofthe air motor 19 and the air chamber 17 and therefore, the air motor 19is not started and the air impact driver can be prevented from beingstarted by erroneously operating the trigger lever similar to themechanical type safety apparatus of the prior art.

Successively, an explanation will be given of the safety measure whenthe contact nose 12 is temporarily pushed and thereafter returned to theinitial position. When pressing is released from the state of pressingthe contact nose shown in FIG. 7, and the spool 23 a of the contactvalve 23 returns to the initial state shown in FIG. 6, pressurized airsupplied to the air chamber of the piston controlling pilot valve 41 andthe air chamber of the air motor controlling pilot valve 39 is exhaustedto the atmosphere via the exhaust path 23 b of the spool 23 a of thecontact valve 23. Thereby, even when the trigger lever 9 is operated,similar to the above-described case of operating to switch ON only thetrigger lever 9, the air cylinder 13 and the air motor 19 are notstarted.

Meanwhile, an explanation will be given of operation of a case of astructure in which different from the above-described contact valve 23,when a contact valve is switched off, secondary side pressure air is notexhausted in reference to FIG. 8 through FIG. 10. Here, a spool 62 of acontact valve 61 is not provided with a path as shown by an initialstate of FIG. 8 through FIG. 9, when the contact valve 61 is opened,similar to the contact valve 23 of FIG. 6 and FIG. 7, pressurized air issupplied to the air chamber of the piston controlling pilot valve 41 andthe air chamber of the air motor controlling pilot valve 39.

Further, when pressing of the temporarily pressed contact nose isreleased to return to the initial position, as shown by FIG. 10, thecontact valve 61 is closed and pressurized air supplied to the airchamber of the piston controlling pilot valve 41 and the air chamber ofthe air motor controlling pilot lever 39 is not discharged. Therefore,when the trigger lever is operated to switch ON under the state, similarto the above-described explanation of the starting operation, the pistoncontrolling pilot valve 41 and the air motor controlling pilot valve 39and the air motor switching valve 33 are made ON and the air cylinderand the air motor 19 are started to inject a screw, however, accordingto the invention, as shown by FIG. 6, when the contact valve 23 isdisposed at a switch-off position, secondary side pressurized air isexhausted to the atmosphere to thereby resolve a danger of wild running.

FIG. 11 through FIG. 4 show other embodiment of a contact valveaccording to the invention, and according to the contact valve 71 shownin FIG. 11, an inner diameter of a lower portion of the cylinder portion72 is made to be larger than an outer diameter of the spool 73.Therefore, when the spool 73 returns to the initial position,pressurized air remaining at the air chamber of the piston controllingpilot valve 41 and the air chamber of the air motor controlling pilotvalve 39 is exhausted to the atmosphere via an exhaust path at aclearance between the lower portion of the cylinder portion 72 and thespool 73. As shown by FIG. 12, when the contact nose is pressed to moveup the spool 73, the lower exhaust path of the cylinder portion 72 iscut by the spool 73 and the pressurized air is supplied to the airchamber of the piston controlling pilot valve 41 and the air chamber ofthe air motor controlling pilot valve 39 to bring about the state ofbeing able to be started by operating the trigger.

The contact valve 81 shown in FIG. 13 and FIG. 14 is formed with thevent hole 83 at a lower portion of the cylinder portion 82 and as shownby FIG. 13, when the spool returns to the initial position, pressurizedair remaining in the air chamber of the piston controlling pilot valve41 and the air chamber of the air motor controlling pilot valve 39 isexhausted to the atmosphere via the vent hole 83. As shown by FIG. 14,when the contact nose is pressed in the spool 84 is moved upward fromthe vent hole 83, the vent hole 83 and the lower port 48 and the outletpath 54 are cut, pressurized air is supplied from the upper port 50 tothe air chamber of the piston controlling pilot chamber 41 and the airchamber of the air motor controlling pilot valve 39 to bring about astate of being able to be started by operating the trigger. In this way,even in the contact valves 71, 81 shown in FIG. 11 through FIG. 14,safety is achieved when the contact nose is temporality pressed andthereafter returns to the initial position.

Further, the invention is not limited to the above-described embodimentsbut can variously be modified within the technical range of theinvention and the invention naturally covers the modifications.

The application is based on Japanese Patent Application (Japanese PatentApplication No. 2001-241323) applied on Aug. 8, 2001 and Japanese PatentApplication (Japanese Patent Application No. 2001-241331) applied onAug. 8, 2001 and contents thereof are incorporated here by reference.

INDUSTRIAL APPLICABILITY

As has been explained above, the safety apparatus of the air impactdriver of the invention is constituted to operate the control valve forstarting the air impact driver by the trigger valve operated by thetrigger lever and the contact valve operated to slide by the contactnose and therefore, the long contact arm reaching the trigger lever fromthe nose of the mechanical type safety apparatus of the background artis dispensed with, the width of the air impact driver can be narrowed tobe able to deal with a corner portion or a location having a narrowwidth at which operation has been difficult in the background art.

Further, different from moving an intermediary member of the arm, thelever or the like by the contact nose, the contact nose is constitutedto operate the valve and therefore, the stroke of the contact nose isextremely shortened and operability and operational efficiency arepromoted.

Further, by arranging the contact nose and the contact valve to beproximate to each other, various effects are achieved such that theguide for guiding a member for connecting the contact nose and thecontact valve is dispensed with and a concern of bringing about afailure in sliding by clogging a plaster powder or the like at the guideportion is resolved.

1. A safety apparatus of an air impact driver comprising: a contact noseslidable relative to a nose; a contact valve connected to the contactnose; a trigger valve operated by a trigger lever; a starting controlvalve; and an air pressure logic circuit for controlling the startingcontrol valve using the trigger valve and the contact valve; whereinsaid safety apparatus is provided with a pneumatic signal to start theair impact driver when the trigger valve and the contact valve areswitched to ON positions by pressing the contact nose and pulling thetrigger lever.
 2. The safety apparatus of an air impact driver accordingto claim 1, wherein the contact valve is switched by sliding the contactnose.
 3. The safety apparatus of an air impact driver according to claim1, wherein the contact valve is a switch valve communicating a secondaryside outlet to a primary side inlet when the contact valve is disposedat an ON position and communicating the secondary side outlet to anatmosphere when the contact valve is disposed at an OFF position.